1. Field of the Invention
The present invention generally relates to the mounting and support of hard disk drives for computers and, in a preferred embodiment thereof, more particularly relates to apparatus for removably supporting a plurality of hot plug-connected hard disk drives.
2. Description of Related Art
Hard disk drives for a file server or other type of computer are often mounted, in a vertically or horizontally stacked array, in a rectangular sheet metal xe2x80x9ccagexe2x80x9d structure which may be disposed within the computer housing or externally thereto. For operational convenience and flexibility, each disk drive is typically xe2x80x9chot plugxe2x80x9d connected within the cage. This type of electrical connection permits any of the supported disk drives to be removed and re-installed within the cage without disturbing the operation of the other disk drives.
To effect this desirable hot plug connection of each of the disk drives, each disk drive is typically supported on a carrier structure which is slidably and removably insertable into the cage to mate an electrical connector carried on a rear portion of the drive or its carrier structure with a corresponding electrical connector on a back plane circuit board suitably supported at the rear interior side of the cage.
An increasing problem associated with the carrier support of disk drives removably mounted in cage structures or the like is the control of vibrational forces generated by the drives during their operationxe2x80x94particularly the self-induced oscillatory vibrational forces centered about the axis of rotation of the drive platter. When this type of vibrational force is substantial enough it causes an undesirable degradation in drive performance by increasing the drive seek time for either reading or writing data.
More specifically, in modern high speed hard disk drives, the track density (tracks per inch) at which the data is written has also correspondingly increased. At these high speeds and track densities, disk spindle imbalance forces and rotating actuator resultant forces cause internally generated vibrations that can degrade the data input/output performance of the drive. The actuator pivots about an axis and thus is sensitive to even low levels of vibration. If the actuator misses its seek during data transfer, one or more seek retries are required to complete its command. The extra time for he seek retries causes unwanted and preventable performance degradation of the drive.
This vibration-caused problem was not particularly significant in older, slower speed drives since the mass and physical geometries of the drives and most conventionally used drive carriers offered sufficient built-in damping of the self-induced operational drive vibration about the rotational axis of the drive platter. However, modern high performance hard disk drives now have spin rates in the 7,200 RPM to 12,000 RPM rangexe2x80x94rotational rates which can cause substantial vibration-caused drive performance degradation if the vibrational forces are not appropriately controlled.
One previously proposed approach to protecting a carrier-supported high speed disk drive of this type from vibration-caused performance degradation has been to simply provide heavier and longer drive carriers which have a natural tendency to reduce this vibrational energy due to their substantially increased mass that absorbs more of such energy. However, this increase in carrier size and mass undesirably increases the overall spatial envelope of each drive/carrier assembly with the result that the drives cannot be positioned in as dense an array as smaller drive/carrier assemblies.
Another previously proposed approach to protecting a carrier-supported high speed disk drive of this type from vibration-caused performance degradation has been to position a resilient vibration absorbing structure between the disk drive and its supporting carrier structure. While this approach does not require that the size of the carrier structure be increased, it does undesirably increase the height (and thus the overall volume) of the drive/carrier spatial envelope.
From the foregoing it can be seen that a need exists for improved apparatus for substantially reducing the vibration-caused performance degradation of a carrier-supported hard disk drive of the type generally described above. It is to this need that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a computer system is provided which includes a CPU unit having a microprocessor and a data storage section operative to store data retrievable by the microprocessor. The data storage section includes a housing structure in which a stacked series of data storage devices, illustratively hot-pluggable hard disk drives, are removably supported using specially designed carrier structures upon which the individual disk drives are mounted.
The carrier structures are configured to cooperate with the housing structure in a manner substantially preventing performance degrading, self-induced oscillatory rotational vibrational vibration of the stacked disk drives, during operation thereof within the housing structure, about the rotational axes of the disk drives.
In a preferred embodiment thereof, each carrier structure includes a body removably insertable into the housing structure to a supported operating position therein, and a fastening structure for anchoring the carrier structure to its associated disk drive. A vibration control structure is associated with each carrier structure body and is operative to create between the housing structure and the inserted body generally opposing interference fits that substantially inhibit rotational vibratory oscillation of the inserted body, and thus the disk drive anchored thereto, relative to the housing structure about the rotational axis of the disk drive.
Preferably, each carrier body has front and rear end portions, is rearwardly and removably insertable into the housing structure, and has spaced apart opposite side portions extending in a front-to-rear direction between the front and rear end portions. The opposing interference fits between the body and the housing structure are created by opposing projections formed on these side portions and corresponding inward projections formed on opposing side wall portions of the housing structure. The opposing housing body side portion projections are offset in a front-to-rear direction relative to the rotational axis of the disk drive anchored to the carrier, and is preferably offset in a forward direction relative to such rotational axis.
By creating these opposed interference fits between the carrier structure bodies and the housing structure, performance degrading self-induced oscillatory operational vibration of the disk drives about their rotational axes is substantially inhibited without the necessity of increasing the size and masses of the carrier structures or providing them with space-consuming resilient vibration isolation structures between the disk drives and their associated carrier structures.